Manufacture of sheets or films of compositions containing cellulose esters or ethers



Oct. 4, 1932. A. R. WICKHAM 1,881,108

MANUFACTURE OF SHEETS 0R FILMS OF COMPOSITIONS CONTAINING CELLULOSE ESTERS OR ETHERS Filed NOV. 18, 1931 7 Patented Och-4, 1932 UNITED STATES ALFRED ROBERT WICKHAM, or snws'ron, ENGLAND, ASSIGNOR T srxonns LIMIT D,

I OF LONDON, ENGLAND, A BRITISH COMTANY I v MANUFACTURE OF SHEETS OR FILMS OF COMPOSITIONS CONTAINING CELLULOSE ESTERS 0R ETHERS Application filed November 18, 1931, Serial No. 575,938; and in Great Britain December 22,- 1930-.

sheet or film, after it leaves the surface on' which it is formed through a space maintained charged with water-vapour at a tem' perature considerably above room-temperature. 1

This treatment, which is hereinafter referred tov as the maturing treatment, is for the purpose of removing electrostatic charge and traces of solvent from the film. The maturing temperature is of the order of 100 F., and I have found that if the film is wound at the actualmaturing temperature, it takes several hours to cool down, owing to its low thermal conductivity. Further the film is in a comparatively soft condition as a result of the maturing treatment, and it is found that when the film is subsequently unwound in order to trim it, the edges of adj acent convolutionstend to stick'together, and the action ofparting themcauses an electrostatic charge to be'imparted to the film, which is highly undesirable. It is among the objects of the present invention to provide means whereby these disadvantagesmay be overcome.

This invention provides an improvement in or modification of that contained in the specification of H. J. Hands No. 238,150 filed 6th December, 1927, which consists in winding the film, immediately after the maturing treatment, in a space which is maintained at a temperature considerably below the maturing temperature.

The film is wound at a temperature which i l is approximately 40 F. below thematuring temperature. Alternatively the winding of the film may be effected in two stages, the temperature of the film being first of all reduced by winding at a temperature about 15 F. below the maturing temperature and then by a further 25F. by rewinding at the appropriate temperature.

The invention also provides apparatus for winding the film after the maturing treatment, which comprises a trough, means for winding the film on a spindle contained in said trough, and a cooling jacket surrounding the trough. The jacket may conveniently be constituted by pipes through which cooling water is circulated. A practical embodiment of the apparatus according to the invention will now be de'- scribed by way of example, with reference to the. accompanying diagrammatic drawing. The apparatus consists'of a semi-cylindrical trough 2,.provided'with a jacket through which cooling water may be circulated. The cooling water may be run directly through the jacket or alternatively pipes may be provided within the walls of the trough for the circulation of the water. The trough is provided, with a hinged lid 4. The lid 4 is not provided with cooling pipes, as otherwise vapour would tend to condense thereon and drip on to the film. The lid is therefore conveniently formed of two members having an air space between them. The end walls of the trough are provided with vertical slots 5,, extending from the top of each wall to approximately half-way down the trough. These slots form bearlngs for a longitudinal spindle 6, on which the film 7 is wound, the spindle thus being easily removable fromthe L trough.

The spindle may conveniently be driven mechanically, either by a belt and pulleyor by suitable gearing.

The cold water inlet 8 for the jacket 3 is '85 arranged at the bottom of the trough, and the outlet 9 from the jacket is at the top. By suitable adjustment of the rate of flow of the cooling water, the temperature within the trough is maintained at about 65 F. .A draw-ofi cock 10 is provided at the bottom of the trough to enable any condensate forming thereon to be removed. 1 i i y winding the film in the apparatus according to the invention, it ischanged from '1 the comparatively soft and unstable state in which it leaves the maturing process to a hard cool condition.

When the whole of the film has been wound on the spindle, the latter may be removed 100 from the trough. and may immediately be unwound. There'is, therefore, no need for the film to beleft for any length of time to cool, as was heretofore the case; nor is there any tendency for adjacent. convolutions of the film "to stick together when it is Wound upor for electrostatic charge to be generated.

when it is unwound. I V v It is to be understood that'it issometimes V V preferable to wind the film after maturing in I two stages; In'thisc ase two cooling trough-s 7 j p of the kind illustrated in the drawing are employed, In the first trough the cooling water is arranged tobe at a temperature such that. rthe film is reduced from the maturing tem- 1 "p'erature of 1059: F. to a temperature of about 9091?. The film is then 'rewoun'd in a second cooling trough in which the temperature of the cooling wateris such that the tempera- 2Q ture of the film isreducedto about65 F.

I claim v p 1 p 1. A methodfor the manufacture of films of compositions containing an'organic de-V, rivativ-e of cellulose which comprises in com bination the steps of-applying' to atravelling surface asolution of the aforesaid composition, effecting evaporation of the solvent from-"said 'solution stripping from the surface the film of compositionleft thereon by 0 the evaporation of said solvent, maturing the film by leading it through a. space'maintained charged with water vapour at a temperature considerably abovev room 1 temperature, and immediately thereafter winding the film in a space which-is maintained at atemperature" V considerably below-that of the space in which the a-foresaidmaturing treatment is carried out. 1 1 r "2, A method for the manufacture of films 40 of compositions containing an organic de rivative of cellulose which comprises in com- 7 bination the stepsof applying to a travelling surface a solution of-the aforesaidcom position; effecting evaporation of the solvent I from said solution, stripping from the surface .the film .of composition left thereon by the evaporation of said solvent,rmaturing:the v i film b'y leading it through a space maintained V V chargedwith Water vapourat a temperature 5 considerably above room temperature, and immediately thereafter winding the film first at a temperature of about 15 F bel'ow, the temperature of the space in which the afore-- said maturingtreatment is carried out and then rewinding it at a temperature of about 409 below the maturing temperature. 7 In testimony whereof I aifix my signature. a ALFRED ROBERT WICKHAMQ 

